From: Johan Eriksson <johan@...>
Date: 2008-04-26T06:38:58+09:00
Subject: Re: undefined local variable

Hi --

David A. Black wrote:
> Hi --
> 
> On Sat, 26 Apr 2008, Johan Eriksson wrote:
> 
>> Hi --
>>
>> David A. Black wrote:
>>> Hi --
>>>
>>> On Sat, 26 Apr 2008, Johan Eriksson wrote:
>>>
>>>> Chris Hulan wrote:
>>>>> On Apr 25, 11:16 am, Johan Eriksson <jo...@johaneriksson.se> wrote:
>>>>>> Hi!
>>>>>>
>>>>>> I have some troubles with this.
>>>>>>
>>>>>>            obj_as_list.each do |att|
>>>>>>              if att[1].is_a?(String)
>>>>>>                att[1] = "'#{att[1]'"
>>>>> You're missing a '}' here ----------^
>>>>>
>>>>> does that help?
>>>>>
>>>>
>>>> Nope. I am providing the surrounding function here. (It is defined 
>>>> inside a class.)
>>>>
>>>>    def load_from_file(filename)
>>>>      require 'yaml'
>>>>      yaml_dict = YAML::load(File.open(filename))
>>>>      object_list = []        #The list that should be returned
>>>>      yaml_dict[yaml_dict.keys[0]].each do |yaml_obj|
>>>>        new_obj = self.class.new
>>>>        yaml_obj.each do |obj|
>>>>          obj_as_list = obj.to_a
>>>>          obj_as_list.each do |att|
>>>>            if att[1].is_a?(String)
>>>>              att[1] = "'#{att[1]}'"
>>>>            end
>>>>            str = "new_obj.#{att[0]} = #{att[1]}"
>>>>            eval(str)
>>>>          end
>>>>        end
>>>>        object_list << new_obj
>>>>      end
>>>>      object_list
>>>>    end
>>>>
>>>> And the error:
>>>>
>>>>     NameError: undefined local variable or method `att' for main:Object
>>>
>>> If att[1] is, say, :att, then "#{att[1]}" is "att" and you've got a
>>> dangling att. The whole eval thing seems extremely fragile (which eval
>>> things usually are). I imagine there's a more robust and probably
>>> shorter way to do this, but I'm not sure what the data coming in and
>>> out are supposed to be like.
>>>
>>>
>>> David
>>>
>>
>> I am almost positive that there is, given that I'm pretty much a noob 
>> at ruby. The whole thing is a class_eval too. The idea is to add this 
>> function to a class that has just been created based on a textfile. 
>> The function will receive a file that includes a yaml description of 
>> instances of the class, and the function then makes these instances 
>> and sends them back as a list. I think some fragility is okay, though 
>> I'd be keen on learning better ways to do this. Around the entire 
>> function is
>>
>> the_class.class_eval %{
>>     the function...
>> }
>>
>> I am confused about why it doesn't work though.
> 
> Can you give some sample YAML input? I'm still not quite picturing it.
> 
> 
> David

This is a simple example:

dogs:
     - name        : Fido
       age         : 2

     - name        : Rufus

     - name        : Doggie
       age         : 4

     - name        : Puppy
       age         : 1

The function should then create four instances of dog, assign them the 
names and ages specified, put them in a list and return them.

Thanks for taking the time to help me out!

/Johan